Methods of securing together sections of pipe and fastening flanges and glands are highly developed. The bell flange of one pipe and the gland on an adjoining pipe are usually held together by bolts and nuts. Such a pipe joint is illustrated in U.S. Pat. No. 3,374,012 to Metcalfe et al and this invention is an improvement on that joint.
Often it is necessary or desirable to use tie rods to connect the two pipe components themselves (as distinguished from the connection between the flanged bell formed on the end of one pipe component and the gland which simply encircles the end of the other pipe component). Such tie rods are desirable to oppose the tendency of internal fluid pressure to cause separation of adjoining pipes at the joints. The force tending to separate the pipe sections is the pressure times the maximum cross-sectional area at the joint. Tie rods are also desirable for the reason that they are able to span intervening coupling flanges of such other pipe installations as valves, T-fittings and the like.
The tie lug herein described and claimed constitutes an improvement in the art because, not only does it anchor a tie rod in an improved manner, thus preventing relative movement among the sections of pipe, but it also effects a better seal for the joint to which it is attached. The tie lug performs these several functions in a much simpler and more effective manner than does the prior art.
P. D. Dilley in U.S. Pat. No. 3,010,736 discloses a rod bracket for use in anchoring tie rods. In column 3, line 2 of his patent, Dilley states that an unexpected advantage of his invention is the increased pressure on the packing ring used to seal the joint. Dilley's invention does sucessfully anchor tie rods and does increase the pressure on the packing ring; however, there are several weaknesses in Dilley's bracket which the inventor was unable to eliminate. All forces created by the tightening of the nut on the end of the tie rod and the nut on the end of the T-bolt are exerted on the head of the T-bolt, which in turn is pulling against the threads on the T-bolt nut. The threads of the single T-bolt holding the bracket in place are thus subjected to a high shearing stress. The is an unfortunate situation, for should the T-bolt fail, not only would the tie rod become unanchored, but the joint would become substantially weakened and might leak. Also, Dilley's bracket is formed with a special aperture which requires that a special T-bolt be used for connecting the bell flange to the gland rather than the standard bolt which is used at other points on the same joint.
C. S. Stephens in U.S. Pat. No. 3,144,261 discloses an eye-bolt securing device for use in anchoring the ends of tie rods. It would seem that by tightening the nuts on the end of the tie rod one would also increase the pressure of the gland on the packing. However, the problem inherent in this invention is that the eye portion of the bolts are incapable of withstanding high tension. When a high pressure is exerted on the joint or a strong force on the tie rod, the eye bolts will pull open because of their open stems.